Yukitaka Isa

Accuracy and repeatability of blood volume measurement by pulse dye densitometry compared to the conventional method using 51Cr-labeled red blood cells

AbstractObjective: To determine the accuracy and repeatability of pulse dye densitometry (PDD) in measuring blood volume (BV) by comparing it with the conventional method using 51Cr-labeled red blood cells (RI method) and by assessing sequential measurements. Design: Prospective clinical study. Setting: University hospital. Patientsandparticipants: Eleven adult ICU patients who received cardiac surgery (1st ICU day). Interventions: None. Measurementsandresults: After injecting indocyanine green (10 or 20 mg) into the right atrium, its arterial concentration was continuously monitored at the nose and finger by PDD, and BV was calculated by back extrapolating the logarithmic dye concentration on the dye elimination curve between 2.5 and 5.5 min after mean transit time to each mean transit time with the least squares method. These measurements were repeated in eight patients and performed only once in the other three, and the BV was measured concurrently by the RI method one time. The Bland-Altman method was used for evaluating differences between methods and within methods. The (percentage) biases and standard deviations between the PDD and RI methods and between the successive measurements by PDD at the finger and nose were 0.26±0.49 l (8.8±15.3%) and 0.004±0.25 l (0.06±5.9%) with the probe on a nostril, and 0.16±0.56 l (2.5±14.4%) and 0.19±0.31 l (4.7±7.3%) using the finger probe. The bias between methods was less than 10%, and the repeatability of PDD was better. Conclusions: As PDD can measure BV with good repeatability and with a small bias compared to the RI method, serial changes in BV can be evaluated at the bedside of critically ill patients noninvasively and repeatedly.

The disruptive effects of ketamine on passive avoidance learning in mice : involvement of dopaminergic mechanism

The involvement of dopaminergic mechanisms in ketamine-induced disruption of one trial step-through passive avoidance performance was assessed through the coadministration with the dopamine D1 antagonist SCH 23390, the dopamine D2 antagonist YM-091512 and the dopamine autoreceptor agonist at low doses, apomorphine, in mice. Pretraining (10 min before) administration of ketamine (0; saline, 2.5, 5 and 10 mg/kg SC) dose-dependently reduced the latency in the retention trial conducted 24 h after the training. However, ketamine did not affect the retention latency when administered immediately after the training or prior to retention. YM-09151-2 (0.01 and 0.03 mg/kg SC) and apomorphine (0.01 and 0.03 mg/kg SC), but not SCH 23390 (0.01 and 0.03 mg/kg SC), ameliorated the impaired reduction by ketamine (10 mg/kg) in a dose-dependent manner. These results suggest that ketamine obstructs the acquisition of the passive avoidance task, and that this effect is induced by stimulation of dopamine D2 receptors through dopamine release from the presynaptic terminals.

A comparative study of the vasodilator effects of prostaglandin E1 in patients with pulmonary hypertension after mitral valve replacement and with adult respiratory distress syndrome

To determine whether the vasodilator effects of prostaglandin E1 (PGE (1)) differ according to the etiology and pathophysiology of pulmonary hypertension, we studied 30 patients with pulmonary hypertension after mitral valve replacement (MVR) (n = 16) or with the adult respiratory distress syndrome (ARDS) (n = 14).PGE (1) was administered to decrease the mean pulmonary artery pressure to below 30 mm Hg in both groups. Cardiac index and oxygen delivery tended to increase, whereas mean systemic artery pressure, mean pulmonary artery pressure, systemic vascular resistance index (SVRI), and pulmonary vascular resistance index (PVRI) significantly decreased in both groups. A vasodilatory index was defined in this study to allow evaluation of vasodilation relative to PGE1 dose: systemic vasodilatory index (VIs) = SVRI change/PGE1 dose; and pulmonary vasodilatory index (VIp) = PVRI change/PGE1 dose. The VIp was similar in both groups, but the VIs was significantly greater in the ARDS group compared with the MVR group (13.3 +/- 7.8 vs 4.8 +/- 5.1, P < 0.01). A good correlation was found between the pretreatment intrapulmonary shunt fraction (Qs/Qt [%]) value and PGE1 extraction rate in the lung (r = 0.60), and between the pretreatment Qs/Qt value and PGE1 concentration in the radial artery (r = 0.65) in an additional 15 patients. We conclude that the vasodilator effects of PGE1 on the pulmonary circulation are similar in the two groups, whereas the vasodilator effects on the systemic circulation are significantly greater in the ARDS group and that significant reduction in VIs in the ARDS group was associated with decreased PGE1 extraction in the lung. Implications: Pulmonary hypertension after mitral valve replacement, or with adult respiratory distress syndrome, is a major medical problem. The authors found that administration of prostaglandin E1 significantly dilated the pulmonary circulation with a concomitant decrease in pulmonary artery pressure. Because the systemic vasodilatory effect was greater in the adult respiratory distress syndrome group, the authors concluded that prostaglandin E1 concentrations in the systemic circulation depend on the severity of lung injury. (Anesth Analg 1997;85:507-13)

Accuracy of carboxyhe-moglobin dilution method for the measurement of circulating blood volume

Purpose: The management of circulating blood volume (BVc) is crucial in intensive care unit (ICU) patients. The purpose of this study was to verify the accuracy and precision of the carbon monoxide-labeled hemoglobin (CO-Hb) dilution method (CO method) by comparing it with the51Cr-labeled erythrocyte dilution method (51Cr method) for the measurement of BVc.Methods: A prospective study was performed in 18 patients who underwent coronary artery bypass grafting (CABG) under mild hypothermic cardiopulmonary bypass (CPB). The BVc was measured by both the CO method and the51Cr method at 24 hr after ICU admission in order to verify the accuracy and precision of the CO method. Paired data were assessed in absolute terms, and percentage errors were calculated by the degree of agreement.Results: Small mean differences and standard deviations between the CO method and the51Cr method (−70.2±184.8 mL) and small percentage errors (−0.49±1.29%) indicated the accuracy and precision of the CO method, and a close correlation was observed (r=0.97).Conclusion: The CO method can measure BVc with a similar degree of accuracy as the51Cr method. It is simple, repeatable and safe without the risk of exposure to radioactivity in the ICU.RésuméObjectif: La gestion du volume du sang circulant (VSc) est cruciale chez les patients des unités de soins intensifs (USI). Nous avons voulu vérfier, pour la détermination du VSc, la justesse et la précision de la méthode de dilution avec oxyde de carbone et hémoglobine marquée (méthode CO) en la comparant à la méthode avec des hématies marquées par le51Cr (méthode51Cr)Méthode: Une étude prospective a été réalisée auprès de 18 patients qui subissaient un pontage aortocoronarien avec circulation extracorporelle (CEC) légèrement hypothermique. Le VSc a été mesuré selon les deux méthodes 24 h après l’admission à l’USI. Les données appariées ont été évaluées en valeur absolue et le pourcentage d’erreur a été calculé par le degré de concordance.Résultats: De faibles différences moyennes et écarts types entre la méthode CO et la méthode51Cr (−70,2±184,8 mL) et de bas pourcentages d’erreur (−0,49±1,29%) ont indiqué la justesse et la précision de la méthode CO, et une corrélation étroite a été observée (r=0,97).Conclusion: La méthode CO peut servir à mesurer le VSc avec un degré d’exactitude semblable à celui de la méthode51Cr. Elle est simple, répétable et sécuritaire, sans risque d’exposition à la radioactivité dans l’USI.

Clinical results of extracorporeal membrane oxygenation (ECMO) support for acute respiratory failure: a comparison of a centrifugal pump ECMO with a roller pump ECMO.

PurposeThe purpose of this study was to compare the clinical results of extracorporeal membrane oxygenation (ECMO) using a centrifugal pump (CP group) and that using a roller pump (RP group) for the treatment of acute respiratory failure (ARF).MethodsFrom November 1990 to July 2001, the ECMO system was introduced for the treatment of 15 patients with ARF; 10 cases of pneumonia or adult respiratory distress syndrome (ARDS), 4 cases of pulmonary hemorrhage, and 1 case of hypoxemia following cardiac surgery. Five patients were included in the RP group, and 10 were included in the CP group.ResultsThe mean PaO2/FIO2 ratio, PaCO2 prior to ECMO induction, and the mean duration of ECMO support were 59.8, 38.8 mmHg, and 125 h, respectively, in the RP group, and 65.6, 82.0 mmHg, and 107 h, respectively, in the CP group. The mean PaCO2 value was significantly (P ≪ 0.05) higher in the CP group than in the RP group due to the ventilation with “permissive hypercapnia.” In the RP group, all patients died of either complications or recurrence due to ARF. In the CP group, 3 patients including 2 with pulmonary hemorrhaging were discharged.ConclusionsAlthough the centrifugal pump ECMO improved the clinical results of ARF, the overall prognosis nevertheless depended on the original disease.

Second gas effect of N2O on oxygen uptake.

Purpose: The concept of the second gas effect is well known, however, there have been no studies that showed the relationship between alveolar oxygen concentration and arterial oxygen tension (PaO2) after the inhalation of nitrous oxide (N2O) in humans. The purpose of this study was to examine the changes in both end-tidal oxygen fraction (FETO2) and PaO2 after N2O inhalation in patients under general anesthesia.Methods: Fifteen patients scheduled for elective orthopedic surgery were enrolled in this study. Anesthesia was maintained with the continuous infusion of propofol and with nitrogen (N2) and oxygen (O2) (6 L·min−1, F1O2, 0.33). In all patients, the lungs were ventilated with a Servo 900C ventilator equipped with a gas mixer for O2, N2O, and N2. After obtaining baseline data, N2 was replaced with N2O maintaining F1O2 constant at 0.33. The changes in fractional concentration of O2, N2O, and N2 were continuously measured using mass spectrometer in a breath-by-breath basis. PaO2 and hemodynamic data were obtained at 1, 5, 10, 30 and 60 min after the start of N2O inhalation.Results: Five minutes after N2O inhalation, FETO2 increased from 0.27±0.01 to 0.31±0.02 (P<0.01) and PaO2 increased from 172.0±22.5 mmHg to 201.0±10.3 mmHg (P<0.01). These effects produced by N2O were observed for 30 min.Conclusions: These results confirm the concept of second gas effect of N2O on oxygen uptake in humans and provide evidence that the PaO2 increase correlated with the increase in FETO2 after N2O inhalation.RésuméObjectif: Le concept de l’effet du deuxième gaz est bien connu, mais aucune étude n’a montré la relation qui existe entre la concentration alvéolaire d’oxygène et la pression artérielle d’oxygène (PaO2) à la suite d’inhalation de protoxyde d’azote (N2O) chez l’humain. L’objectif de la présente étude était d’examiner les changements de la fraction d’oxygène de fin d’expiration (FETO2) et de PaO2 après l’inhalation de N2O chez des patients sous anesthésie générale.Méthode: Admis pour une intervention orthopédique planifiée, 15 patients ont participé à l’étude. L’anesthésie a été maintenue avec une perfusion continue de propofol et un mélange azote-oxygène (6 L·min−1, F1O2, 0,33). La ventilation pulmonaire a été assurée par un ventilateur Servo 900C muni d’un mélangeur de gaz pour O2, N2O, et N2. Après l’obtention des données de base, N2 a été remplacé par N2O, maintenant ainsi la F1O2 constante à 0,33. Les changements de concentration fractionnaire de O2, N2O, et de N2 ont été mesurés continûment, pour chaque respiration, en utilisant un spectromètre de masse. On a noté la PaO2 et les paramètres hémodynamiques à 1, 5, 10, 30 et 60 min après le début de l’inhalation de N2O.Résultats: Cinq minutes après l’inhalation de N2O, la FETO2 a augmenté de 0,27±0,70 à 0,31±0,22 (P<0,01) et la PaO2 s’est élevée de 172,0±22,5 mmHg à 201,0±10,3 mmHg (P<0,01). Ces effets produits par le N2O ont été observés pendant 30 min.Conclusion: Les résultats confirment le concept de l’effet du deuxième gaz lié au N2O sur le captage d’oxygène chez l’humain et ils prouvent que l’augmentation de la PaO2 est en corrélation avec l’élévation de la FETO2 après l’inhalation de N2O.

Comparison of the hemodynamic effects of amrinone in patients who required low-to-moderate-dose and high-dose catecholamines after cardiac valve replacement.

OBJECTIVES To determine hemodynamic response to amrinone in patients after cardiac surgery, in relation to the postoperative cardiac function, which was indicated by the required doses of catecholamines. DESIGN Prospective clinical study. SETTING Surgical intensive care unit in a university hospital. PATIENTS Fourteen patients who required a low-to-moderate dose of dopamine and dobutamine (group L) and 14 patients who required a high dose of dopamine and dobutamine (group H) after cardiac valve replacement. INTERVENTIONS A loading dose of amrinone (0.75 mg/kg) was administered during a 15-min period and the continuous infusion was followed incrementally by doses of 5, 10, and 20 microg/kg/min every 60 mins on the first postoperative day. MEASUREMENTS AND MAIN RESULTS Hemodynamic variables were determined by the radial and pulmonary artery catheters at a dose of 0, 5, 10, and 20 microg/kg/min. Two-way repeated-measures analysis of variance showed significant interaction in the two groups in cardiac index and mean systemic arterial pressure. Cardiac index increased in a dose-dependent manner in group L but was unchanged in group H. Systemic vascular resistance index decreased in a dose-dependent manner in both groups. The mean systemic arterial pressure decreased in group L at a dose of 5 microg/kg/min and returned to the baseline level at doses of 10 and 20 microg/kg/min. On the other hand, the mean systemic arterial pressure significantly decreased in group H at a dose of 20 microg/kg/min. CONCLUSIONS The inotropic effects of amrinone after cardiac valve replacement may be associated with the postoperative myocardial reserve, which was indicated by the required doses of catecholamines, although a similar vasodilative effect was observed in both groups.

Changes in gastric intramucosal pH and circulating blood volume following coronary artery bypass grafting

Purpose: To determine the changes in gastric intramucosal pH (pHi) following coronary artery bypass grafting (CABG) in comparison with systemic hemodynamic variables and circulating blood volume (BVc).Methods: Twenty patients who underwent CABG under mild hypothermic cardiopulmonary bypass (CPB) were included. Hemodynamic variables and the values of pHi were obtained at 3, 6, 12 and 24 hr after admission to the intensive care unit (ICU). The pHi was measured by gastric tonometric catheter. The BVc was measured by carbon monoxide (CO)-labeled hemoglobin (CO-Hb) dilution method (CO method) at 6 and 24 hr after ICU admission.Results: Systemic vascular resistance index (SVRI) and pulmonary vascular resistance index (PVRI) decreased with time. Systemic oxygen delivery index (DO2I) and systemic oxygen consumption index (VO2I) showed a gradual increase during the study period. By contrast, pHi decreased to the lowest value (7.26±0.05) at six hours and returned to normal levels (7.34±0.04) at 24 hr after ICU admission. Changes in BVc between six and 24 hr ranged from −242 ml to 978 ml (mean, 334±338 ml). The pHi increased in patients whose BVc increased by >300 ml. Mean fluid balance was negative in this period (−386±667 ml; range, −1786− + 423 ml).Conclusion: The pHi showed the lowest value at six hours and returned to normal at 24 hr after ICU admission. The pHi increased with the decrease in vascular resistance and with the increases in BVc in this period. The improvement of pHi, an indicator of splanchnic perfusion, appears to be related to systemic vasodilatation and an increase in BVc.RésuméObjectif: Déterminer les changements de pH gastrique intramuqueux (pHi) qui suivent un pontage aortocoronarien, comparés aux variables hémodynamiques générales et au volume sanguin circulant (VSc).Méthode: Vingt patients qui ont subi un pontage aortocoronarien sous circulation extracorporelle (CEC) légèrement hypothermique ont participé à l’étude. Les variables hémodynamiques et le pHi ont été mesurés à 3, 6, 12 et 24 h après l’admission à l’unité des soins intensifs (USI). La mesure du pHi a été faite avec un cathéter gastrique tonométrique. Le VSc a été mesuré par la méthode de dilution de l’hémoglobine marquée à l’oxyde de carbone (CO-Hb), à 6 et à 24 h après l’admission à l’USI.Résultats: L’indice de résistance vasculaire générale (IRVG) et l’indice de résistance vasculaire pulmonaire (IRVP) ont baissé en fonction du temps. L’indice de distribution d’oxygène générale (DO2I) et l’indice de consommation d’oxygène générale (VO2I) ont affiché une augmentation graduelle pendant l’étude. Par ailleurs, le pHi a présenté sa plus basse valeur (7,26±0,05) à six heures et est revenu à la normale (7,34±0,04) à 24 h après l’admission à l’USI. Le VSc s’est modifié entre 6 et 24 h, de −242 ml à 978 ml (moyenne, 334±338 ml). Le pHi s’est élevé chez les patients dont le VSc a augmenté de > 300 ml. Le bilan hydrique moyen a été négatif pendant cette période (−386±667 ml; limites, −1786− +423 ml).Conclusion: Le pHi le plus bas a été noté à 6 h et est revenu à la normale à 24 h après l’admission à l’USI. Le pHi a augmenté selon la baisse de résistance vasculaire et l’augmentation du VSc pendant ce temps. L’amélioration du pHi, un indicateur de perfusion splanchnique, semble relié à une vasodilatation générale et à une augmentation du VSc.

In patients with adult respiratory distress syndrome, initial responders to inhaled nitric oxide did not show better outcome than nonresponders.

We examined data from 29 patients fulfilling the American-European Consensus Conference definition of ARDS who underwent NO inhalation from 1997 to 2001. The University Institutional Review Board approved this therapy for patients with ARDS. Written informed consent was obtained from each patient’s family to examine their records. Patients with immunosuppression and advanced malignant disease were excluded. All patients required mechanical ventilation with a Siemens Servo 300 ventilator (Siemens, Danvers, MA, USA), in a volume-controlled ventilation mode and with a positive end-expiratory pressure (PEEP) of 10–15cmH2O. We kept peak airway pressures below 50cmH2O and applied tidal volumes of 8–10 ml·kg 1. The target oxygenation parameters were PaO2 above 60mmHg and arterial oxygen saturation (SaO2) above 90%. To achieve sufficient removal of carbon dioxide we adjusted the ventilatory rate to 40 breaths/min. If hypercapnia developed, we accepted levels of PaCO2 below 50mmHg. All patients were sedated with propofol infusions, and muscle relaxation was achieved with vecuronium when necessary. NO was delivered through the ventilator, using a bleed-in adapter placed in the inspiratory limb of the circuit, just distal to the humidifier. NO was supplied from tanks containing 812ppm, with the remaining gas being nitrogen (Taiyo-Toyo, Kanagawa, Japan). The NO and NO2 concentrations were continuously monitored using an NO/NO2 Gas Monitor (TMS-100R; Taiyo-Toyo). Gas samples were withdrawn a short distance proximal to the patient’s endotracheal tube, ensuring that a length of 100cm was maintained between the central NO instillation and the withdrawal of gas for analysis. The analyzers were regularly calibrated at 0 and 10ppm NO and 0 and 4 ppm NO2. The exhaled gas was scavenged with an NO nitric oxide scavenger system.

Alteration of regional brain oxygen saturation (rSO2) in a patient with cerebral damage after aortic arch replacement: carbon dioxide reactivity monitored by near-infrared spectroscopy suggested inverse steal phenomenon

Cerebral damage is a major complication of aortic arch replacement [1]. To monitor the cerebral circulation and cerebral tissue oxygenation during the perioperative period, several invasive and noninvasive monitors have been devised. Although there are some controversies regarding interpretation of the data [2,3], nearinfrared spectroscopy is reported to enable physicians to detect intracranial phenomena, such as cerebrovascular alterations or tissue oxygenation status, noninvasively [4-6]. Recently, several reports have noted that cerebrovascular response to carbondioxide could be detected by this spectroscopic method [7-11]. Although hyperventilation induces vasoconstriction in cerebral tissue and decrease of regional brain oxygen saturation (rSO2), we studied a case in which rSO 2 increased after hyperventilation.